ARMY TM 9-6115-464-34
AIR FORCE 35C2-3-445-2
NAVY NAVFAC P-8-624-34
(19)
(20)
(21)
(22)
(23)
(24)
(25)
(26)
(27)
(28)
Install blower and coupling disc assembly on a dymetric balance machine and check both static and
dynamic balance. Unbalance shall not exceed 0.5 inch-ounce in either plane. Balance blower and
coupling disc assembly as outlined in step (26) below.
Use a double bridge to measure resistance of each phase of exciter rotor. Resistance of each phase
shall be 0.1473 to 0.1627 ohm at 77°F (25°C). Difference between phase reading shall not exceed 2
percent.
Using 374 megger, ground test exciter by applying 300 Vac at 60 Hz RMS for 1 second between one
terminal and ground (frame). There shall be no evidence of dielectric breakdown.
Using a double bridge measure resistance between terminals of exciter stator, Resistance shall be
4.50 to 5.50 ohms at 77°F (25°C).
Using 374 megger tester, ground test stator assembly by applying 750 Vac at 60 Hz RMS for one
second between all leads (tied together) and the frame. Apply 500 Vac at 60 Hz RMS for one second
between phases with neutral open. There shall be no indication of dielectric breakdown in either test.
Use semiconductor test set to test rectifiers for inverse current leakage at peak recurrent voltage of
600 volts. Leakage shall not exceed 20.0 milliamperes at 77°F (25°C). Check forward voltage drop.
Voltage drop shall not exceed 1.2 volts at 77°F (25°C ).
If rotor and balance assembly is out of balance, add or subtract balance weights until remaining
unbalance in both balance planes does not exceed 0.5 ounce-inch. Once rotor and balance
assembly is balanced, tach weld balance weights and attaching screw.
If blower and coupling disc assembly is out of balance, correct by machining material from inner
diameter of blower as required. Remaining unbalance shall not exceed 0.5 inch-ounce in both
balance plans.
If damage to the stator windings is discovered during inspection and test, rewind using figure 3-142
(figure 3-143 for 400 Hz) as a guide.
After rewinding, vacuum impregnate the stator assembly as follows:
(a) Place wound stator in an oven at 300°F (-0, +15°F (149°C) for 120 ± 10 minutes.
(b) Transfer stator to vacuum tank.
NOTE
Do not allow temperature of stator to drop below 125°F.
(c) Evacuate tank to a maximum of 50 mm Hg absolute and hold for 10 minutes (minimum).
(d) Without breaking the vacuum, introduce varnish (Military Specification MIL-I-24092, Type M, Class
155) to a sufficient depth to completely cover the stator. Hold vacuum for 5 minutes (minimum).
(e) Break vacuum and hold at atmospheric pressure for 5 minutes (minimum).
(f) Return varnish to storage tank and allow the stator to drain.
(g) Place the impregnated stator in an oven at 300°F, -0°F, +15°F, (149°C) for 120 ± 10 minutes.
(29) If damage to rotor core windings is discovered at inspection and test, rewind in accordance with
figure 3-144 (figure 3–145 for 400 Hz).
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